Ink jet printhead cartridges typically use thin film circuitry with electrical contact points to provide power and communication for printing operations. Thin film circuits are used because they are very small, which is desired for the ink ejection portion of the printhead. Communications are used to instruct the ink ejection portion of the printhead to fire ink drops with thin film firing resistors of the circuit. These contact points are very small and have to be precisely positioned. As such, in many cases, each contact point is manufactured with close mechanical registration.
However, ink appearance at the printhead near the thin film circuitry during printing can occur under certain circumstances and has been one of the most influential factors affecting printhead reliability. Namely, ink accumulation can penetrate through the circuit traces and cause an electrical short, thereby rendering the printhead inoperable. To avoid this, thin film circuits typically have core protective layers that are usually non-permeable. Nevertheless, ink penetration can still occur from a side of the circuit, through an edge of a ground trace, and then to the active trace.
In addition, if a firing resistor in the thin film circuit blows or becomes damaged, protective layers of the circuit can be breached, thereby exposing the underlying circuitry to electrical shortage. Basically, the resistors in the thin film circuitry are arranged in discrete groups known as primitives. Each primitive has a number of resistors receiving signals from a controller through a common connection or bus that routes power to the thin film resistors residing in the primitive. Consequently, if one resistor in the primitive has an electrical short, the electrical short can be transferred to other resistors in the primitive, and to other primitives linked by the same bus.
Therefore, what is needed is a system and method that protects the printhead from ink, namely a printhead with increased protection from corrosion so that other components of the thin film circuitry are protected during ink leaks.